fix stack

lib/compress.js

@@ -2584,7 +2584,8 @@ merge(Compressor.prototype, {
                     });
                 }
             });
-            tt.stack = compressor.stack.slice(); // so that's able to see parent nodes
+            // allow transform() to view the whole AST
+            tt.stack = compressor.stack.slice(0, -1);
             self = self.transform(tt);
         } catch(ex) {
             if (ex !== self) throw ex;